Multicellular tumor spheroids (MTS) grown in vitro are used as a model system for solid tumors growing in vivo, testing quantitatively the effects of chemotherapeutic drugs mostly but also X rays and other agents and modifiers, by correlating damage to MTS growth and survival with dose. By varying dose (concentration x time) and fractionation regimes of adriamycin (ADR), 5 FU and other drugs in common clinical use and correlating this with damage to MTS, treatments (dose, regimes) that give maximal damage for minimal dose will be sought. Growth curves after treatment, which permit measurement of depth and duration of growth depression ("regression") and time for recovery of growth ("recurrence time"), will be correlated with dose and treatment regime of drugs to find optimal schedules for repeated treatments. Effect on MTS of diagnostic and therapeutic ultrasound exposure, within and beyond the range used clinically will be tested, with and without in-beam oscillation during exposure.